Depending on whether you have a bonnet liner or not- 30 seconds to 5 minutes.
It really is a mod you can do in your !Removed! break.
The only thing that may slow it down a bit is if the nozzle is a heated one and the wires on the ones you source are not long enough, in that case it's maybe 5 - 10 minutes to splice in extension wires.

Fitted mine the weekend, they are a great job and save so much more water. Great guide :)

Thanks Stephen mate,Ive found they create a nice foam effect on the windscreen when driving over 50kmh/40mph As you said they use less water or the expensive ready mix pink fluid from halfords.This modification will pay for itself.

Excellent guide as usual Lenny. Got myself a pair today and the whole process took about 10 min. That was because I had the jet facing the wrong way at first. Quickly rectified and all working. Much nicer and efficient than the jet types.